Measurement of environmental pollutants using passive sampling devices--a commentary on the current state of the art

Passive sampling devices have been used since the 1970s to measure time-weighted average (TWA) or equilibrium concentrations of pollutants in various environmental matrices (e.g. air, soils and sediments and water). In recent years the popularity of using such samplers has increased and the technology in now well established for the measurement of atmospheric pollutants. This sector has a long experience of using passive samplers in the short- and long-term assessment of air quality in the local environment and on a global scale (e.g. within the United Nations Stockholm Convention on the trans-boundary movement of persistent organic pollutants (POPs) where large networks of samplers on a continental scale have been established). In comparison, the use of passive samplers for monitoring the aquatic environment has been slower to take off. There has, however, been a recent research drive to develop devices for measuring the wide range of pollutants that can be found in environmental waters (e.g. ground, surface, and marine). It is now being recognised that passive samplers can play a valuable role in monitoring water quality within a legislative framework such as the European Union's Water Framework Directive (WFD). The data from these devices can be used alongside the results obtained from conventional spot or bottle sampling to improve risk assessments and to inform decisions on undertaking potentially expensive remedial actions. Such monitoring techniques may have uses within the European Registration, Evaluation, Authorisation & restriction of CHemicals (REACH) Directive and the forthcoming European Marine Strategy Directive. It is expected that the aquatic monitoring sector will follow a transition similar to that which occurred in air monitoring where data obtained from passive samplers can use used within a legal framework. There has also been increased interest in extending the role of passive samplers to both the measurement of equilibrium concentrations and investigating the movement and release of the dissolved fraction of various pollutants in the pore water of sediments and soils.     

Reasonable creatures: rights and rationalities in valuing the countryside

Debate on the economic valuation of the countryside is typically polarized between absolutist critics who would deny it any valid role and equally fervid proponents who see its techniques as the only way of integrating the environment into policy making. Such debate is structured by conflicting notions of rights, responsibilities and values, rather than by consideration of the role of technique in practical policy‐making. This paper attempts to take the debate forward and begins by examining the ways in which rights, responsibilities and values have been historically created. The techniques of economic valuation rest on particular conceptions of these, making them irreducibly political, and at the same time their results are often used to justify political decisions. Yet the proper role of technique ought to be to explore options. Provided that the sort of clarification that economic valuation offers is understood, it may, along with other types of technique, be used to open up the decision making process.     

Diving of the sea snake Pelamis platurus in the Gulf of Panamá

The horizontal movement patterns of eleven yellow-bellied sea snakes [Pelamis platurus (Linnaeus)] were determined incidentally to acoustic tracking studies of their diving behavior in the Gulf of Panamá during 1983–1985. The average speed of the snakes was 1.9 km h^-1 (range 0.3 to 7.1 km). Movement direction is influenced by phasic northsouth tidal currents and secondarily affected by combinations of factors that affect local current velocity. The velocity of diving snakes did not always agree with that observed for the surface current. Drift rate was not correlated with average or maximum dive depth, however, snakes that surfaced to breathe one or more times during a period had greater average drift rates than those that did not surface. The role of such factors as feeding, predator avoidance, thermoregulation, orientation, and the avoidance of surface turbulence are considered in a discussion of the adaptive significance of diving for P. platurus. Diving in this species may enable it to avoid surface disturbance, facilitate relative position changes within the surface drift, and contribute to various aspects of its feeding behavior.     

Zooplankton capture by two scleractinian corals,Madracis mirabilis andMontastrea cavernosa,in a field enclosure

Capture of zooplankton by scleractinian corals has been noted for several species, yet quantitative information on rates of capture and differential capture by prey taxon has been lacking. We used field enclosures to examine prey capture for two coral species,Madracis mirabilis (Duchassaing and Michelotti) andMontastrea cavernosa (Linnaeus), on the north coast of Jamaica (Discovery Bay) in November 1989, February and March 1990, and January 1992.M. mirabilis has small polyps and a branching colony morphology (high surface/volume ratio), whereasM. cavernosa has large polyps and mounding colonies (low surface/volume ratio). Corals were isolated front potential prey, then were introduced into enclosures with enhanced zooplankton concentrations for 15- to 20-min feeding periods. Corals were fixed immediately after the experiment to prevent digestion, and coelenteron contents were examined for captured zooplankton. Plankton pumps were used to sample ambient zooplankton in the enclosures near the end of each run. Selectivity and capture rates were calculated for each prey taxon in each experiment; both indices were high for relatively uncommon large prey, and low for copepods, which were often the most common items in the plankton. Sizes of zooplankton captured by both species were generally larger than those available considering all prey taxa combined, but were almost the same for both coral species, even though the corals' polyp sizes are very different. This occurred primarily because small copepods, with low capture rates, dominated most plankton samples. For specific prey species, or group of species, there were few significant differences in size between the prey available and the prey captured.M. mirabilis, with small polyps, also captured far more prey per unit coral biomass than didM. cavernosa, with much larger polyps. We hypothesize that the large differences in capture rate of prey taxa are related to escape or avoidance behavior by those potential prey, and to the mechanics of capture, rather than to any selectivity by the corals.     

Conservation and the 4 Rs,which are rescue,rehabilitation, release,and research

Vertebrate animals can be injured or threatened with injury through human activities, thus warranting their “rescue.” Details of wildlife rescue, rehabilitation, release, and associated research (our 4 Rs) are often recorded in large databases, resulting in a wealth of available information. This information has huge research potential and can contribute to understanding of animal biology, anthropogenic impacts on wildlife, and species conservation. However, such databases have been little used, few studies have evaluated factors influencing success of rehabilitation and/or release, recommended actions to conserve threatened species have rarely arisen, and direct benefits for species conservation are yet to be demonstrated. We therefore recommend that additional research be based on data from rescue, rehabilitation, and release of animals that is broader in scope than previous research and would have community support.     

Use of a physiologically based extraction test to estimate the human bioaccessibility of potentially toxic elements in urban soils from the city of Glasgow,UK

A simple, two-stage, physiologically based extraction has been applied to assess the human bioaccessibility of potentially toxic elements (PTE) in 20 urban soils from a major UK city. Chromium and iron bioaccessibilities were found to be markedly higher in the intestinal phase, whilst lead and zinc bioaccessibilities were higher in the stomach. Copper and manganese bioaccessibilities were generally similar under both extraction conditions. Principal component analysis was used to study relationships amongst bioaccessible element concentrations and land use. Distinctions could be observed between the distributions of the urban metals—copper, lead and zinc—and metals predominantly of geogenic origin, such as iron. There was no clear delineation between roadside soils and soils obtained from public parks. Bioaccessible analyte concentrations were found to be correlated with pseudototal (aqua regia soluble) analyte concentrations for all elements except iron. Results of the BCR sequential extraction did not, in general, provide a good indication of human bioaccessibility. Comparison of bioaccessible PTE concentrations with toxicological data indicated that lead is the element of greatest concern in these soils but that levels are unlikely to pose a health risk to children with average soil intake.     

The stress of scramble: sex differences in behavior and physiological stress response in a time-constrained mating system

Iteroparous species maximize lifetime reproductive fitness by balancing current and future reproductive investments. In order to maximize fitness in the face of social or environmental heterogeneity, individuals of the same species may vary in whether they prioritize current reproductive opportunity or sacrifice immediate reproduction in order to prioritize survival and future reproductive potential. Glucocorticoid (GC) secretion plays an important role in mediating this trade-off by promoting behavioral and physiological responses associated with survival, often at the expense of nonessential (e.g., reproductive) functions. We used wood frogs (Lithobates sylvaticus [Rana sylvatica]) to test whether males and females differed in their (a) physiological response (plasma corticosterone [CORT] concentration) to standardized handling stress—a proxy for predation threat—and (b) performance of reproductive behaviors that may enhance their conspicuousness to predators. We also tested whether levels of male competition influenced sex differences in these factors, as more intense competition may require males to devote more time to risky reproductive behaviors. We found that females had lower baseline CORT but exhibited a significantly greater CORT response to a stressor and spent less time performing potentially risky behavior (surface floating) than did males. These sex differences were consistent across different levels of male mating competition. Our results reveal that during breeding, males and females may differentially respond to stressors and perform risk-prone behaviors, despite facing the same extreme breeding constraints, providing new insight into the survival-reproduction trade-off of explosively breeding species.     

Contrasting nitrate adsorption in Andisols of two coffee plantations in Costa Rica

Fertilizer use in coffee plantations is a suspected cause of rising ground water nitrate concentrations in the ground water-dependent Central Valley of Costa Rica. Nitrate adsorption was evaluated beneath two coffee (Coffea arabica L.) plantations in the Central Valley. Previous work at one site had identified unsaturated zone nitrate retardation relative to a tritium tracer. Differences in nitrate adsorption were assessed in cores to 4 m depth in Andisols at this and one other plantation using differences in KCl- and water-extractable nitrate as an index. Significant adsorption was confirmed at the site of the previous tracer test, but not at the second site. Anion exchange capacity, X-ray diffraction data, extractable Al and Si, and soil pH in NaF corroborated that differences in adsorption characteristics were related to subtle differences in clay mineralogy. Soils at the site with significant nitrate adsorption showed an Al-rich allophane clay content compared with a more weathered, Si-rich allophane and halloysite clay mineral content at the site with negligible adsorption. At the site with significant nitrate adsorption, nitrate occupied less than 10% of the total anion adsorption capacity, suggesting that adsorption may provide long-term potential for mitigation or delay of nitrate leaching. Evaluation of nitrate sorption potential of soil at local and landscape scales would be useful in development of nitrogen management practices to reduce nitrate leaching to ground water.     

Pollution and Waste Production in Home-Based Enterprises in Developing Countries: Perceptions and Realities

Using mainly qualitative data from a four country case study, this paper describes the nature of home-based enterprises (HBEs) and the wastes that they produce. It finds that most only generate material similar to domestic wastes, but in greater quantities. While some are undoubtedly generating dangerous wastes, they are only a small proportion of all HBEs and tend to be aware of at least some of the problem and take mitigating steps. The paper argues that the encouragement of clean processes should replace the usual negative views about HBEs that are held by policy makers.